1. Field of the Invention
The present invention relates to a time-division decimation filter bank, in which filtering and decimation operations of a decimation filter unit can be performed by time-division.
2. Description of Related Art
During signal transmission, some signals are converted into a digital format for transmission by using high-density sampling points. However, at a receiving end, the signal has to be first filtered and decimated in frequency, and then the transmitted data is obtained. Generally, the frequency decimation has four stages, i.e. a 16-fold decimation is performed.
FIG. 1 is a schematic diagram illustrating a conventional filter and decimation structure. Referring to FIG. 1, in view of a frequency domain, an input signal is input with a frequency of fs, and is decimated in frequency for four stages through four decimation filter units 100, and a frequency of an output signal is fs/16. The decimation filter unit 100, for example, includes of a half band filter (HBF) and a decimator. The decimator is represented by a downward arrow. In other words, each of the decimation filter units 100 performs a decimation sampling of fs/2, so that the four decimation filter units 100 can totally reach a decimation sampling of fs/16. Regarding an output, the decimation filter unit 100 of each stage can provide an input of the decimation filter unit 100 of a next stage, and can simultaneously provide the output to a time-division multiplexer (MUX) 102, and then an output data is selected by time-division according to a control signal 104.
Regarding an actual data, for example, during a satellite communication, one data consists of a real part data and an imaginary part data, which are respectively referred to as I data and Q data. According to the conventional structure of FIG. 1, 16 decimation and filter units 100 are required to reach a 4-fold decimation of the I data and the Q data, which may lead to a high cost.
To achieve an effective filtering and decimation design is one of major research and development directions.